Evaluation of beta-cypermethrin for the control of Triatoma infestans

This study assessed the insecticidal effect in the laboratory and in the field of the new pyrethroid beta-cypermethrin against Triatoma infestans, the vector of Chagaś disease, and compared it with that of deltamethrin. Comparison of the 50% lethal dosis (LD50) of both pyrethroids showed that beta-cypermethrin is more effective against the nymphs and that deltamethrin is more effective against the adults. Evaluation of the 50% lethal concentration (LC50) of the flowable formulations of both insecticides, placed on different surfaces, showed that their effectiveness on glass is similar, while on a ceramic surface deltamethrin is slightly more effective. The flowable formulations of the two insecticides were tested in 100 infested homes in the province of Santiago del Estero, Argentina. Deltamethrin was applied at a surface concentration of 25 mg/m2 and beta-cypermethrin at 50 mg/m2. The real surface concentrations of these products were analyzed from filter paper samples placed on walls and ceilings. Gas chromatography revealed good agreement with the target concentrations. In addition, entomological assessments were carried out 60, 90, 180, and 365 days after the treatments. Infestations were found only during the last assessment: in the peridomiciliary area of 10% of the houses treated with beta-cypermethrin and in 7% of the houses treated with deltamethrin (6% in the peridomiciliary area and 1% inside the house). The results indicate that beta-cypermethrin's effectiveness in controlling T. infestans when applied at a concentration of 50 mg/m2 is similar to that of deltamethrin applied at a concentration of 25 mg/m2.